Dual fuel engine system and method for controlling a dual fuel engine system

Abstract

A method for controlling a dual-fuel engine system includes estimating a total indicated engine load, the total indicated engine load being based on a sum of measured engine power and a power loss estimate. The method further includes determining a total fueling amount based on engine speed and the total indicated engine load, the total fueling amount including a fueling amount for a first fuel and a fueling amount for a second fuel. The method also includes controlling the dual-fuel engine system using the total fueling amount.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application Nos. 17 / 944,910, 17 / 944,900, and 17 / 944,905, each filed September 14, 2022, the entire contents of each of which are incorporated herein by reference.

[0002] The present disclosure relates generally to a method for controlling a dual fuel engine system. [Background technology]

[0003] Generally, a dual fuel engine system may include an original equipment manufacturer (OEM) machine control system, a base engine control system or module (ECM) operably coupled to the OEM, and a gas control system operably coupled to both the OEM machine control system and the base engine control system. Summary of the Invention [Means for solving the problem]

[0004] One aspect of the present disclosure relates to a method for controlling a dual-fuel engine system. The method includes estimating a total indicated engine load, where the total indicated engine load is based on a sum of measured engine power and a power loss estimate. The method further includes determining a total fueling amount based on engine speed and the total indicated engine load, where the total fueling amount includes a fueling amount for a first fuel and a fueling amount for a second fuel. The method also includes controlling the dual-fuel engine system using the total fueling amount.

[0005] Another aspect of the present disclosure relates to a method for controlling a dual-fuel engine system. The method includes estimating a total indicated engine load, the total indicated engine load being based on a sum of measured engine power, a friction force estimate, and an auxiliary power estimate. The method further includes determining a total fueling amount from a first lookup table, the lookup table being based on engine speed and the total indicated engine load. The method also includes determining at least one updated total fueling amount based on the total fueling amount and an operating state of a dual-fuel mode switch in the dual-fuel engine system. The method further includes determining a control input for at least one actuator in the dual-fuel engine system, the control input being based on selecting a corresponding set of lookup tables associated with the at least one actuator, the set of lookup tables including a plurality of lookup tables, each of the plurality of lookup tables being based on engine speed and the at least one updated total fueling amount.

[0006] Another aspect of the present disclosure relates to a dual-fuel engine system including an internal combustion engine operable in a dual-fuel mode, at least one actuator operably coupled to the internal combustion engine, and at least one controller in communication with the internal combustion engine and the at least one actuator. The at least one controller is configured to receive a first input corresponding to engine speed and a second input corresponding to measured engine power output, calculate a power loss estimate, determine a total fueling amount based on the measured engine power output and the power loss estimate, determine a first fuel command for a first fuel associated with the internal combustion engine based on at least the calculated speed governor command and the power loss estimate, and determine at least one updated total fueling amount based on the total fueling amount and the first fuel command for the first fuel. The at least one controller is further configured to select a lookup table set associated with the at least one actuator based on a second fuel displacement rate associated with the internal combustion engine, the lookup table set being based on the engine speed and the at least one updated total fuel supply amount, and send an input to the at least one actuator based on the lookup table set.

[0007] One aspect of the present disclosure relates to a method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel. The method includes determining a frictional power loss of an internal combustion engine of the dual-fuel engine system, the frictional power loss being based on an engine speed of the internal combustion engine and a frictional torque estimate. The method further includes determining an accessory power loss of an output of the internal combustion engine, the accessory power loss being based on the engine speed and the accessory torque estimate. The method also includes estimating a net engine power output based on the accessory power loss and a shaft power output of the internal combustion engine. The method also includes estimating an indicated power output for the first fuel and estimating the first indicated engine power output and a first power output for the second fuel based on the estimated net engine power output.

[0008] Another aspect of the present disclosure relates to a method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel. The method includes estimating a net engine power output of an internal combustion engine of the dual-fuel engine system based on an incidental power loss of the internal combustion engine's power output and an estimated shaft power output of the internal combustion engine. The method also includes determining a first total indicated engine power output based on the net engine power output and a frictional power loss of the internal combustion engine. The method further includes determining a lower heating value (LHV) for the second fuel in the internal combustion engine, the LHV being a measured or estimated value. The method also includes estimating a second total indicated engine power output based on the LHV, the total flow estimate for the second fuel, and the power estimate for the first fuel. The method further includes initiating at least one engine protective measure based on a difference between the first total indicated engine power output and the second total indicated engine power output being greater than a predetermined threshold.

[0009] Another aspect of the present disclosure relates to a dual-fuel engine system operable in a dual-fueling mode. The system includes at least one controller in communication with an internal combustion engine configured to operate using a first fuel and a second fuel. The at least one controller is configured to receive an input corresponding to an engine speed of the internal combustion engine, receive an input for calculating a net engine power output estimate, and calculate a percent rated power output of the internal combustion engine based on the engine speed and the net engine power output estimate. The at least one controller is further configured to determine a base substitution rate target for the second fuel for the internal combustion engine based on the engine speed, the percent rated power output, an intake manifold temperature in the internal combustion engine, and a knock tendency index estimate in the internal combustion engine. The at least one controller is also configured to determine a second fuel output target for the internal combustion engine based on the base substitution rate target for the second fuel and the first indicated engine power output estimate.

[0010] One aspect of the present disclosure relates to a method for controlling a dual-fuel engine system configured to operate using a first fuel and a second fuel. The method includes determining a flow rate target for a second fuel for an internal combustion engine of the dual-fuel engine system, the flow rate target for the second fuel being based on an output target for the second fuel of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine. The method also includes adjusting the flow rate target for the second fuel based on at least one of a measured second fuel temperature or a measured second fuel injector pressure. The method further includes determining at least one base second fuel injector command based on the adjusted flow rate target for the second fuel, the estimated second fuel displacement ratio, and the second fuel displacement ratio target. The method also includes determining second fuel injector commands for at least one engine bank based on the at least one base second fuel injector command.

[0011] Another aspect of the present disclosure relates to a dual-fuel engine system for an internal combustion engine configured to operate using a first fuel and a second fuel. The dual-fuel engine system includes at least one injector for the second fuel operably coupled to an internal combustion engine having a left bank and a right bank, the internal combustion engine being operable in a dual-fuel mode. The dual-fuel engine system also includes at least one proportional-integral-derivative (PID) controller communicatively coupled to the internal combustion engine and the at least one injector for the second fuel. The at least one PID controller is configured to receive a feedforward input, a second fuel displacement ratio estimate, and a second fuel displacement ratio target. The at least one PID controller is further configured to output at least one injector command for the second fuel based on the feedforward input and to bias the at least one injector command for the second fuel to each of the right bank and the left bank based on an exhaust temperature differential associated with each of the right bank and the left bank.

[0012] Another aspect of the present disclosure relates to a dual-fuel engine system operable in a dual-fuel mode. The dual-fuel engine system includes an internal combustion engine having at least one engine bank, the internal combustion engine configured to operate using a first fuel and a second fuel. The dual-fuel engine system also includes at least one injector for the second fuel operably coupled to the internal combustion engine and at least one controller communicatively coupled to the internal combustion engine and the at least one injector for the second fuel. The at least one controller is configured to determine a second fuel flow target for the internal combustion engine, the second fuel flow target being based on a second fuel output target for the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine. The at least one controller is further configured to adjust the second fuel flow target based on at least one of a measured second fuel temperature or a measured second fuel injector pressure to determine an adjusted second fuel flow target for the dual-fuel mode. The at least one controller is also configured to determine at least one base second fuel injector command based on the adjusted second fuel flow target, the displacement rate estimate for the second fuel, and the displacement rate target for the second fuel. The at least one controller is further configured to determine an injector command for the second fuel for the at least one engine bank based on the at least one base second fuel injector command.

[0013] This summary is illustrative only and should not be construed as limiting.

[0014] The present disclosure will become more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements and in which: [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram of a dual fuel engine system according to an exemplary embodiment. [Figure 2] FIG. 2 is a block diagram of a control system for the dual fuel engine system of FIG. 1 according to an exemplary embodiment. [Figure 3] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 4] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 5] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 6] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 7] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 8] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. [Figure 9] 3 is a flow chart illustrating a method performed by the control system of FIG. 2 according to an exemplary embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the following detailed description, reference is made to the accompanying drawings, which form a part of this specification. In the drawings, like symbols generally identify like components unless the context dictates otherwise. The exemplary embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, generally as described herein and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are contemplated and make a part of this disclosure.

[0017] The present disclosure relates, at least in part, to systems and methods that result in reduced operating costs, improved efficiency, and / or improved performance of dual-fuel engine systems. In some embodiments, such systems and methods enable meeting target emission levels. In some embodiments, protocols for control of the dual-fuel system are adjustable to streamline interfacing between, for example, a diesel engine ECM, a gas controller, and an OEM controller. In various embodiments, the dual-fuel engine system (and related operating methods) is tailored to maximize the use of less expensive gas fuels and minimize the use of diesel fuel while meeting performance and emission requirements and maintaining robust engine protection. Specifically, precise and robust control of the dual-fuel engine system is required to meet Tier 4 emission regulations with the dual-fuel engine system. Such precise and robust control includes, but is not limited to, control of the gas or liquid fuel system, the second fuel type system (e.g., diesel, gas, etc.), and the aftertreatment system included within the dual-fuel engine system. The present disclosure outlines systems and methods for precise and robust control of a dual-fuel engine system, including accurately determining (e.g., by measuring or estimating) multiple engine parameters (e.g., shaft power, friction, auxiliary power, first fuel (e.g., diesel, gas, liquid fuel) power, second fuel (e.g., gas, liquid) power, second fuel (e.g., gas, liquid) displacement ratio, fuel quality parameters associated with the second fuel (e.g., methane number), LHV, second fuel (e.g., gas, liquid) temperature, second fuel (e.g., gas, liquid) pressure, knock intensity, exhaust temperature, etc.) and using the determined parameters as inputs to determine appropriate commands for one or more actuators in the dual-fuel engine system. The systems and methods described herein are applicable to new engine builds or for retrofitting onto existing Tier 4 diesel engine systems.Advantageously, the systems and methods described herein are less costly and complex than typical port gas injection or cylinder pressure sensing systems.

[0018] Referring to FIG. 1 , a block diagram of a dual-fuel engine system 10 is shown according to an exemplary embodiment. The dual-fuel engine system 10 is configured to be an engine with a dual-fuel operating mode, where the engine is configured to operate using two different fuels. The engine can be configured to operate using a first fuel and a second fuel, where the first fuel and the second fuel have different properties and / or chemical compositions. The properties can include autoignition temperature, flame speed, etc. The fuels can include, for example, diesel and natural gas. For example, the first fuel can be diesel fuel. The second fuel can be, for example, natural gas, e-fuel, or a liquid biofuel. The liquid biofuel can be, for example, methanol and / or ethanol. The first fuel or the second fuel can be any one of diesel, gas-to-liquid (GTL) diesel, heavy fuel oil (HFO), low sulfur fuel oil (LFSO), hydrotreated vegetable oil (HVO), marine gas oil (MGO), renewable diesel, biodiesel, paraffinic diesel, a high-cetane fuel such as dimethyl ether (DME), F-76 fuel, F-34 fuel, Jet A fuel, JP-4 fuel, JP-8 fuel, or oxymethylene ether (OME), or a low-cetane fuel (e.g., high-octane fuel, high-methane fuel). The low-cetane fuel can be natural gas, hydrogen, ethane, propane, butane, synthetic gas, ammonia, methanol, ethanol, or gasoline. The first fuel and / or the second fuel may optionally be a blend of fuels. It should be appreciated that the above are merely example fuels, and other types of first and second fuels are not excluded. In various embodiments, the dual-fuel engine system 10 is configured for one or more oil and gas production applications (e.g., on-land oil and / or gas drilling and hydraulic fracturing).

[0019] As shown in FIG. 1 , the dual-fuel engine system includes an internal combustion engine 20 operably coupled to a control system 11 via at least one controller 18. The control system 11, including a machine control system (OEM system) 12, a first fuel control system 14, and a second fuel control system 16, is configured to send one or more inputs to the controller 18, which in turn controls the internal combustion engine 20. In various embodiments, the first fuel control system 14 and its components are configured to operate using a first fuel. In other embodiments, the second fuel control system 16 and its components are configured to operate using a second fuel. For example, in various embodiments, the first fuel control system 14 is a diesel control system and the second fuel control system 16 is a gas control system. In other embodiments, the first fuel control system 14 is a first gas control system and the second fuel control system 16 is a second gas control system. In yet other embodiments, one or both of first fuel control system 14 and second fuel control system 16 may be liquid fuel control systems.

[0020] In yet other embodiments, first fuel control system 14 and its components are configured to operate using the second fuel, and second fuel control system 16 and its components are configured to operate using the first fuel. In still other embodiments, first fuel control system 14 and second fuel control system 16, and their respective components, can each selectively operate using either the first fuel or the second fuel. In various embodiments, first fuel control system 14 and second fuel control system 16 operate cooperatively within internal combustion engine 20.

[0021] In various embodiments, the controller 18 is configured to include a processor and a non-transitory computer-readable medium (e.g., a memory device) having computer-readable instructions stored thereon that, when executed by the processor, cause the at least one controller 18 to perform one or more operations. In various embodiments, the at least one controller 18 is a computing device (e.g., a microcomputer, microcontroller, or microprocessor). In other embodiments, the at least one controller 18 is configured as part of a data cloud computing system configured to receive commands from a user-controlled device and / or a remote computing device.

[0022] While the following description generally relates to a system in which the first fuel control system 14 operates using a first fuel and the second fuel control system 16 operates using a second fuel, it should be understood that in other embodiments, the first fuel control system 14 and the second fuel control system 16 may each be configured to selectively operate using either the first fuel or the second fuel, as described above. The controller 18 is also operably coupled to at least one second fuel injector 28 for facilitating injection of the second fuel, at least one second fuel heater 32 configured to heat the second fuel, and at least one actuator 33. In some embodiments, the second fuel injector 28 is a gas injector. In other embodiments, the second fuel injector 28 is a liquid fuel injector. In various embodiments, the at least one second fuel heater 32 is a gas heater configured to heat a gas. In some embodiments, the at least one second fuel heater 32 is a liquid fuel heater configured to heat a liquid fuel. In other embodiments, the dual-fuel engine system 10 does not include a second fuel heater. In some embodiments, each of the second fuel injector 28, heater 32, and actuator 33 is operably coupled to the internal combustion engine 20. In various embodiments, the second fuel injector 28 is configured to control or facilitate injection of a second fuel (e.g., gas or liquid or a second gas) into the internal combustion engine 20. The at least one second fuel heater 32 is configured to regulate the temperature of the second fuel flowing through the internal combustion engine 20. The actuators 33 may include one or more first fuel type (e.g., diesel type or other liquid type, first gas type) actuators, air handling actuators, aftertreatment actuators, or any other type of actuator within the dual-fuel engine system 10. Accordingly, during operation, the controller 18 can send one or more inputs to one or more of the internal combustion engine 20, the second fuel injector 28, the heater 32, or the actuator 33 to facilitate a desired operating mode of the dual-fuel engine system 10.

[0023] As shown, the internal combustion engine 20 includes an output shaft 24 and may also include one or more accessories 22. The internal combustion engine 20 further includes at least one manifold 26. In various embodiments, the at least one manifold 26 includes, but is not limited to, an intake manifold. The internal combustion engine 20 also includes at least one engine cylinder bank. In some embodiments, the at least one engine cylinder bank includes a left bank 30 and a right bank 31. During operation of the dual-fuel engine system 10, the control system 11 may receive one or more inputs from a user and / or one or more sensors within the dual-fuel engine system 10 and may control the operation of at least one of the internal combustion engine 20, the second fuel injector 28, or the actuator 33 via the controller 18.

[0024] 2 is a block diagram of the control system 11 of the dual-fuel engine system 10, according to an exemplary embodiment. As shown, the OEM system 12 may include one or more sensors 35, each coupled to one or more corresponding components within the dual-fuel engine system 10. In various embodiments, the one or more sensors 35 may be operatively coupled to or in communication with a frac ("frac") pump, accessories, one or more inlets or outlets of the internal combustion engine 20, or any other component within the dual-fuel engine system 10 (e.g., a cooling fan, a flywheel, a brake, etc.). The OEM system 12 may include one or more processors configured to receive inputs from the sensors 35. In various embodiments, the one or more inputs from the sensors 35 may include a power output estimate, a frac pump speed, a frac pump discharge pressure, a dual-fuel mode start request, or any other input detectable by the one or more sensors 35. As shown, the OEM system 12 is communicatively coupled to each of the first fuel control system 14 and the second fuel control system 16, and the OEM system 12 can output information sensed by one or more sensors 35 or receive input from the first fuel control system 14 and / or the second fuel control system 16.

[0025] As shown in FIG. 2 , the first fuel control system 14 includes one or more sensors 40 coupled to or disposed adjacent to one or more components within the internal combustion engine 20. In various embodiments, the one or more sensors 40 may be configured to determine (e.g., sense, detect, measure) at least one of engine speed, intake manifold temperature, engine coolant temperature, oil temperature, cooling fan duty cycle, first fuel (e.g., diesel, first gas, or other liquid) ratio, or an operating state of a dual-fuel mode switch 55. In various embodiments, the dual-fuel mode switch 55 may be configured to switch operation of the internal combustion engine 20 between a single-fuel mode or a dual-fuel mode. Additionally or alternatively, the one or more sensors 40 may be configured to determine a lower heating value (LHV) of the second fuel (e.g., gas, liquid, or second gas). In still other embodiments, the one or more sensors 40 may be configured to determine one or more parameters indicative of the LHV, which may include, but is not limited to, a second fuel (e.g., gas, liquid, or second gas) density or speed of sound. The first fuel control system 14 also includes an engine speed governor 50. In various embodiments, the engine speed governor 50 may include one or more controllers configured to control the speed of the internal combustion engine 20.

[0026] The first fuel (e.g., diesel or first gas) control system 14 also includes a first fuel (e.g., diesel or first gas) engine control system (ECM) and a torque fueling calculation module 45. In various embodiments, the torque fueling calculation module 45 can include one or more processors in communication with one or more reference databases or repositories, the one or more processors configured to reference data stored in the databases to perform torque calculations for the internal combustion engine 20. For example, in various embodiments, the torque fueling calculation module 45 is configured to calculate torque based on one or more known parameters. In various embodiments, the module 45 is configured to receive inputs corresponding to dual-fuel mode operating conditions, engine friction parameters, incidental (“parasitic”) torque parameters, engine speed, OEM mechanical power estimates, and engine incidental power estimates (e.g., gas controller, liquid fuel controller, flywheel, etc.). In various embodiments, the one or more reference databases or repositories can include a lookup table 65. In various embodiments, the one or more lookup tables 65 include one or more chi-tables. In various embodiments, lookup table 65 may include reference information for engine torque, engine speed, engine friction parameters, parasitic or parasitic torque parameters, first fuel (e.g., diesel or first gas) fuel rate, intake manifold temperature, and / or engine coolant temperature. In various embodiments, the engine friction parameters of lookup table 65 may be based on at least one of oil temperature or coolant temperature. In some embodiments, the parasitic or parasitic torque parameters of lookup table 65 may be based on a cooling fan duty cycle (i.e., of a cooling fan in internal combustion engine 20).In various embodiments, module 45 is configured to determine at least one of a total fueling amount of a first fuel (e.g., diesel or a first gas), an approximate equivalent total fueling amount, an equivalent total fueling amount (i.e., a fueling amount of a second fuel equivalent to a fueling amount of a first fuel), a friction torque estimate, or a first fuel rate.

[0027] First fuel control system 14 also includes a first fuel (e.g., diesel or first gas) air handling, aftertreatment, and fuel system reference determination and control module 60. In various embodiments, control module 60 may include at least one processor in communication with a database (e.g., lookup table) 75. In various embodiments, database 75 includes a data repository related to engine speed, fuel delivery (e.g., equivalent total fuel delivery, approximate equivalent total fuel delivery), second fuel (e.g., gas, liquid, or second gas) displacement ratio (G / D), compressor inlet density (CID), or any other relevant parameter. Accordingly, one or more processors within control module 60 are configured to reference data stored in database 75 to determine one or more system inputs for at least one of air handling control system 80, aftertreatment control system 85, or first fuel control system 90. In various embodiments, the one or more system inputs include, but are not limited to, actuator commands or targets (e.g., set points, operating thresholds, etc.) for at least one of the first fuel air handling control system 80, the aftertreatment control system 85, or the first fuel control system 90.

[0028] 2 , the second fuel (e.g., gas, liquid, or second gas) control system 16 may include one or more sensors 95 coupled to or disposed adjacent to one or more components within the internal combustion engine 20. In various embodiments, the one or more sensors 95 may be configured to determine (e.g., sense, detect, measure, etc.) at least one of OEM mechanical torque, accessory torque, a fuel quality parameter associated with the second fuel, second fuel injector pressure, second fuel supply pressure, second fuel flow rate, engine bank exhaust temperature, aftertreatment system temperature, LHV, second fuel temperature, dual fuel mode input, knock intensity, G / D, or any other relevant parameter. In various embodiments, the fuel quality parameter associated with the second fuel may be a knock propensity indicator or knock propensity index. In some embodiments, a knock propensity index (KPI) may be an index correlating a fuel composition (i.e., of the second fuel) with the knock propensity of an engine (i.e., engine 20) operating with the fuel (i.e., the second fuel). In some embodiments, the KPI may be a methane number (MN), an octane number, an anti-knock index (AKI), or any other parameter known in the art. In various embodiments, when the second fuel is natural gas, the KPI may be MN. In various embodiments, when the second fuel is gasoline, the KPI may be octane number or AKI. In some embodiments, the engine bank exhaust temperature may correspond to a left bank average exhaust temperature and / or a right bank average exhaust temperature. In some embodiments, the bank average exhaust temperature may be calculated by averaging measurements from individual exhaust port temperature sensors. In some embodiments, the exhaust port temperature sensor may be among at least one of sensors 35, 40, and / or 95. Second fuel control system 16 also includes an OEM mechanical and accessory power estimation module 130.In various embodiments, OEM mechanical power and accessory power estimation module 130 may include one or more processors configured to estimate OEM mechanical power and / or accessory power based on one or more inputs received by one or more sensors 95 (and / or from sensors 35, 40). In some embodiments, the accessory power may be power associated with one or more accessory components and / or output shafts (e.g., output shaft 24) within dual-fuel engine system 10. In various embodiments, OEM mechanical power and accessory power estimation module 130 is configured to receive inputs related to an OEM mechanical power estimate, accessory torque measurements, pump speed, pump discharge pressure, and engine speed, and the one or more processors then estimate an accessory power estimate based on the inputs. Similarly, second fuel control system 16 also includes a KPI (e.g., MN) estimation module 125. In various embodiments, KPI estimation module 125 may include one or more processors configured to estimate KPIs associated with internal combustion engine 20 based on one or more inputs received by one or more sensors 95 (and / or from sensors 35, 40). In various embodiments, at least one of sensors 35, 40, or 95 may be assigned or partitioned to any of the different control systems within dual-fuel engine system 10 (e.g., OEM system 12, first fuel control system 14, second fuel control system 16) without changing the overall functionality of the sensor. For example, in various embodiments, sensor 95 may be included in or operably coupled to any of OEM system 12, first fuel control system 14, or second fuel control system 16. Similarly, sensor 35 may be included in or operably coupled to any of OEM system 12, first fuel control system 14, or second fuel control system 16. Sensor 40 may also be included in or operably coupled to any of OEM system 12 , first fuel control system 14 , or second fuel control system 16 .

[0029] Second fuel control system 16 also includes an indicated engine power and second fuel (e.g., gas, liquid, or second gas) estimation module 115. Engine power and second fuel estimation module 115 may include one or more processors configured to receive one or more inputs related to the operation of dual-fuel engine system 10. Engine power and second fuel estimation module 115 may be further configured to determine at least one of a thermal efficiency estimate, a first power output estimate of the second fuel (e.g., gas, liquid, or second gas), an indicated power output estimate of the first fuel (e.g., diesel, first gas, or other liquid), a net engine power output estimate, an intake manifold temperature (e.g., maximum intake manifold temperature), and / or other related parameters using database 170 and / or torque-to-power calculation system 175. In various embodiments, database 170 is a look-up table. In some embodiments, torque-to-power calculation system 175 may be or include computer logic. In various embodiments, engine power and second fuel estimation module 115 is configured to receive one or more inputs corresponding to a G / D estimate, a friction torque estimate, a parasitic ("parasitic") torque estimate, a first fuel rate, engine speed, intake manifold temperature, and / or an MN estimate. In embodiments, KPI estimates are determined by KPI module 125. While the terms "torque" and "power" are used in various instances throughout this disclosure, it should be understood that in various embodiments, torque may be used in place of power, or vice versa. For example, it should be understood that power may be calculated from torque and speed, and vice versa. In still other embodiments, any other parameter indicative of load (e.g., as an alternative or in addition to torque and / or power) may be determined and / or used in operations performed by control system 11.

[0030] Second fuel control system 16 also includes a second fuel (e.g., gas, liquid, or second gas) LHV and G / D estimation module 120. LHV and G / D estimation module 120 may include a second fuel (e.g., gas, liquid, or second gas) output selector switch 185, an LHV learning algorithm 180 configured to process one or more received inputs, and an output rationality diagnostic and protection module 190. In various embodiments, LHV learning algorithm 180 includes a filter (e.g., a low-pass filter, a moving average filter, etc.) and / or an adaptive learning routine. In some embodiments, one or more inputs are received from sensor 95. LHV and G / D estimation module 120 may include one or more processors configured to receive inputs including a total flow estimate of the second fuel (i.e., of the second fuel flowing through engine system 10), a thermal efficiency estimate, an indicated power output estimate of the first fuel, and a first indicated engine power output estimate. In various embodiments, one or more processors of LHV and G / D estimation module 120 may receive signals from sensors 35, 40, and / or 95. Thus, LHV and G / D estimation module 120 can estimate G / D and LHV quantities associated with internal combustion engine 20. In various embodiments, one or more processors in LHV and G / D estimation module 120 can determine the LHV and G / D estimates by multiplying the total flow rate estimate of the second fuel by the thermal efficiency estimate and using the result to normalize the first power output estimate of the second fuel (e.g., by dividing the first power output estimate of the second fuel by the product of the total flow rate estimate and the thermal efficiency estimate of the second fuel) to determine an instantaneous LHV quantity. LHV learning algorithm 180 can process the instantaneous LHV quantities to then determine (i.e., learn) the LHV estimates. In various embodiments, the second fuel output selector switch 185 may be configured to receive inputs corresponding to a first power output estimate and a second power output estimate.In some embodiments, the second fuel output selector switch 185 may also be configured to use the first and second output estimates to output a final power output estimate for the second fuel. In various embodiments, the final power output estimate for the second fuel is based on a maximum or minimum value of the first and second output estimates. In various embodiments, the power output rationality diagnostic and protection module 190 may include one or more processors configured to receive inputs corresponding to the first and second indicated engine power output estimates. In some embodiments, the power output rationality diagnostic and protection module 190 is further configured to initiate one or more diagnostic actions or engine protection protocols based on and in response to a comparison of one or both of the first and second indicated engine power output estimates with one or more thresholds.

[0031] As shown, second fuel control system 16 further includes a G / D target self-compensation module 105. In various embodiments, G / D target self-compensation module 105 is configured to adjust or compensate a G / D target of internal combustion engine 20. Module 105 is configured to receive one or more inputs indicative of engine speed, engine load (e.g., power, torque, etc.), intake manifold temperature, and / or KPI estimates. In various embodiments, the one or more inputs are received by module 105 from sensors 95, 35, and / or 40. In some embodiments, the one or more inputs received by module 105 are processed by a speed-based G / D target interpolation unit 135 to determine a G / D target based on an indicated engine speed. In various embodiments, speed-based G / D target interpolation unit 135 determines the G / D target based on an indicated engine speed by using data stored in one or more databases 145. In some embodiments, one or more databases 145 may include one or more look-up tables. Module 105 also includes a G / D target limiter 140 that includes one or more processors configured to determine a G / D target limit based on one or more inputs. In various embodiments, the one or more inputs may include engine knock, exhaust temperature, and / or a first fuel quantity. In various embodiments, the exhaust temperature corresponds to the exhaust temperature of an engine bank. Second fuel control system 16 may use the G / D target limit together with the first indicated engine power estimate to determine a second fuel power target.

[0032] As shown in FIG. 2 , second fuel control system 16 includes second fuel injector control module 110 including at least one G / D proportional-integral-derivative (PID) controller 150. In various embodiments, PID controller 150 is configured to receive a feedforward input, where the feedforward input is based on a second fuel injector pressure and a temperature-compensated second fuel flow target. In various embodiments, second fuel injector pressure and temperature may be measured by sensors 95, 35, and / or 40. Controller 150 may also receive a feedback input corresponding to a G / D estimate and a target input corresponding to the G / D controller. In response to receiving the feedforward input, the feedback input, and the target input, PID controller 150 may output at least one base second fuel injector command. In various embodiments, the at least one base second fuel injector command is related to a second fuel injector command for at least one engine bank. In some embodiments, the second fuel injector command for at least one engine bank includes a left bank second fuel injector command and / or a right bank second fuel injector command.

[0033] Second fuel injector command converter 160 may be operably coupled to PID controller 150. In various embodiments, second fuel injector command converter 160 may include one or more processors configured to convert a base second fuel injector command into a second fuel injector command for at least one engine bank. Second fuel injector control module 110 may also include a bank balancing PID controller 155. In various embodiments, PID controller 155 is configured to receive a feedback input corresponding to a difference in exhaust temperature between a left bank of internal combustion engine 20 (e.g., left bank 30) and a right bank of internal combustion engine 20 (e.g., right bank 31) and a target value related to the exhaust temperature difference. In various embodiments, the target value is zero. In response to the feedback input and the target input, PID controller 155 is configured to output a left bank correction amount and a right bank correction amount. In various embodiments, one or both of the left bank correction amount and the right bank correction amount may be either a positive value or a negative value. The output left bank correction amount and right bank correction amount may each be added to a base second fuel injector command (e.g., output from PID 150), which second fuel injector command converter 160 may convert to respective left bank second fuel injector commands and right bank second fuel injector commands. Second fuel flow estimator 165 is configured to receive each of the left bank second fuel injector command and the right bank second fuel injector command along with the second fuel pressure and the second fuel temperature. In various embodiments, second fuel flow estimator 165 may include or be coupled to one or more processors within module 110. In some embodiments, the second fuel pressure and / or the second fuel temperature are measured by sensors 95, 35, and / or 40. In various embodiments, the second fuel flow estimator 165 is configured to output an overall second fuel flow estimate associated with the internal combustion engine 20 based on the left bank second fuel injector command and the right bank second fuel injector command, the second fuel pressure, and the second fuel temperature.

[0034] Finally, as shown in FIG. 2 , second fuel control system 16 includes a second fuel heater control module 100. In various embodiments, second fuel heater control module 100 is configured to control the operational state of at least one heater 32 coupled to internal combustion engine 20. In various embodiments, second fuel heater control module 100 includes one or more processors configured to receive one or more inputs from at least one controller 18 and / or other components in control system 11. The one or more processors in second fuel heater control module 100 may be configured to cause second fuel heater control module 100 to change the operational state of at least one heater 32. In some embodiments, changing the operational state of at least one heater 32 may include adjusting an operational setting of heater control valve 195 to control the operational state of at least one heater 32. In various embodiments, at least one heater 32 may be an electric heater. In other embodiments, at least one heater 32 may be configured to provide heat using engine coolant.

[0035] In various implementations, the engine control system 11, including the OEM system 12, the first fuel control system 14, and the second fuel control system 16, can cooperate to control the dual-fuel engine system 10. FIG. 3 shows a flow chart illustrating a method 300 for controlling the dual-fuel engine system 10, according to an exemplary embodiment. In operation 305, the engine control system 11 estimates a total engine load (e.g., power, torque, etc.) of the internal combustion engine 20. In various embodiments, the OEM system 12 calculates the total engine load by determining a first load amount ("primary load") transmitted through the engine (e.g., via a flywheel, a fracture pump load, etc.) and broadcasts the determined first load to the first fuel control system 12 and / or the second fuel control system 16 (e.g., via a data link). In embodiments in which OEM system 12 controls an auxiliary load (a "secondary load," e.g., a cooling fan load) in dual-fuel engine system 10, OEM system 12 may estimate the auxiliary load, add the auxiliary load to the first load quantity, and then broadcast (e.g., via a data link) the sum representing the total engine load to systems 14 and / or 16. In operation 310, control system 11 may determine a total fueling amount for internal combustion engine 20. In operation 315, control system 11 may then control dual-fuel engine system 10 using the total fueling amount determined in operation 310.

[0036] In various implementations, the control system 11 can estimate the total engine load (e.g., power, torque, etc.). In some implementations, the control system 11 estimates the total engine load in operation 305 by measuring engine power in operation 320, estimating power loss in operation 325, and determining the sum of the measured engine power and the estimated power loss in operation 330. In some embodiments, the estimated total engine load can be based on input received from the OEM system 12 (e.g., from one or more sensors that may sense at least one of pump discharge pressure, speed, current, or voltage) responsive to or indicative of the external load. The OEM system 12 may then use the input (i.e., the sensed information) to calculate the engine load. The OEM system 12 may then output the calculated load value to the second fuel control system 16 and / or the first fuel control system 14 using a data link signal and / or an analog signal (e.g., 4 mA to 20 mA). In some embodiments, the external load corresponds to at least one of a generator or a pump operably coupled to the internal combustion engine 20. In various implementations, the engine control system 11 can determine the total fueling amount in operation 310. In some implementations, the control system 11 determines the total fueling amount in operation 310 based at least in part on the measured engine speed (335) and the calculated speed governor indicated torque demand (340). As shown in FIG. 4 , in various implementations, controlling the dual-fuel engine system 10 in operation 315 can include determining an updated total fueling amount in operation 345 and determining at least one control input for the at least one actuator 33 in operation 350. In various embodiments, the at least one actuator 33 can be a first fuel system actuator. In various implementations, the updated total fueling amount determined in operation 345 can be based on determining an operational state of the dual-fuel mode switch 55 in operation 355.In various embodiments, the updated fueling amount determined in operation 345 includes a first updated fueling amount and a second updated fueling amount. In some embodiments, the first updated fueling amount corresponds to the maximum between the total fueling amount and the fuel command for the first fuel (e.g., diesel, a first gas, or other liquid). In some embodiments, the second updated total fueling amount is determined by subtracting the fuel command for the first fuel from the first updated total fueling amount to determine a first fuel equivalent amount of the fueling amount of the second fuel, and adding the equivalent fueling amount of the first fuel to the second fuel command for the first fuel.

[0037] In various implementations, determining the control input for the at least one actuator 33 (in Operation 350) can be based on selecting a set of lookup tables. Information in the lookup tables can then be referenced in determining the control input. The lookup tables can include information from one or more of the first fuel ECM and torque fueling calculation module 45, the first fuel / air handling, aftertreatment, and fuel system reference determination and control module 60, and / or the indicated engine power and second fuel power estimation module 115. Selecting the set of lookup tables can be performed in Operation 360. In various embodiments, selecting the set of lookup tables in Operation 360 includes determining a compressor inlet density (CID) of the internal combustion engine 20. In some embodiments, selecting the set of lookup tables in Operation 360 additionally or alternatively includes determining a G / D within the internal combustion engine 20. In other embodiments, selecting the set of lookup tables in Operation 360 additionally or alternatively includes determining an operational state of the dual fuel mode switch 55. In some embodiments, selecting the set of lookup tables in operation 360 includes selecting at least one of an air handling lookup table, an aftertreatment lookup table, or a fueling lookup table.

[0038] In various implementations, control system 11 can determine a maximum amount between the total fueling amount (from operation 310) and the first fuel command for the first fuel. In various embodiments, the first fuel command for the first fuel is determined from first fuel control system 14. In some embodiments, control system 11 can be configured to determine a second updated total fueling amount. In various embodiments, the second updated fueling amount is determined by subtracting the first fuel command for the first fuel from the first updated total fueling amount to determine a first fuel equivalent amount of the fueling amount of the second fuel associated with the internal combustion engine, and adding the first fuel equivalent amount of the fueling amount of the second fuel to the second fuel command for the first fuel to determine a second updated total fueling amount. In various embodiments, control system 11 can determine at least one actuator command based on engine speed and at least one of the first updated total fueling amount or the second updated total fueling amount. In some embodiments, the at least one actuator command may be associated with at least one of the air handling control system 80, the aftertreatment control system 85, an actuator within the first fuel control system 90, or the actuator 33.

[0039] In various embodiments, determining the total fueling amount in operation 310 may include referencing one or more torque-to-fuel lookup tables. In various embodiments, the one or more torque-to-fuel lookup tables are determined or referenced from the first fuel ECM and torque fueling calculation module 45. In various embodiments, the lookup tables may be based on engine speed and a commanded first fuel torque input. In some embodiments, the commanded first fuel torque input may be determined by sensor 35. In various embodiments, the commanded first fuel torque input determined in operation 310 is based on the sum of a friction force estimate and an engine speed torque demand. In some embodiments, the engine speed torque demand corresponds to the difference between the engine speed and a predetermined engine speed target. In various embodiments, the control system 11 determines a power loss estimate in operation 325. In some embodiments, the control system 11 determines the power loss estimate in operation 325 by estimating a friction torque amount associated with the internal combustion engine 20, estimating an accessory torque amount, determining a charge air pumping torque amount, and determining the engine speed. In various embodiments, engine speed is determined via sensors 35, 40, and / or 95. In various embodiments, the amount of charge air pumping torque is an estimate of pumping losses associated with dual-fuel engine system 10, which correspond to the amount of work done by the engine to draw air into the engine to promote combustion and then expel the combustion products into the atmosphere. In some embodiments, the charge air pumping torque may be measured using cylinder pressure data determined during engine development. In various embodiments, the data determined during engine development may be used to calibrate a pumping torque virtual sensor configured to sense the amount of charge air pumping torque (i.e., operably coupled to OEM system 12, first fuel control system 14, and / or second fuel control system 16).

[0040] In some implementations, the friction torque estimate may be determined from a lookup table. In various embodiments, the lookup table is determined or referenced from the first fuel ECM and torque fueling calculation module 45. In some embodiments, the lookup table is based on engine speed and an engine friction parameter. In some embodiments, the engine friction parameter may correspond to an oil temperature or a coolant temperature within the internal combustion engine 20 of the dual fuel engine system 10. In various embodiments, the control system 11 may be configured to determine the accessory torque estimate from a lookup table. In various embodiments, the lookup table is determined or referenced from the first fuel ECM and torque fueling calculation module 45. In some embodiments, the lookup table is based on engine speed and an accessory torque parameter. In various embodiments, the accessory torque parameter may correspond to an amount of cooling fan power (e.g., measured or estimated) or a duty cycle commanded by the internal combustion engine 20 of the dual fuel engine system 10.

[0041] In various embodiments, the control system 11 is configured to determine the first fuel command for the first fuel from a torque-to-fuel lookup table. In various embodiments, the torque-to-fuel lookup table is determined or referenced from the first fuel ECM and the torque fueling calculation module 45. In some embodiments, the torque-to-fuel lookup table is based on engine speed (i.e., of the internal combustion engine 20) and a friction force estimate and a torque demand associated with the internal combustion engine 20. In various implementations, the torque demand is set by the engine speed governor 50.

[0042] In various embodiments, the control system 11 may be configured to initiate one or more protective measures associated with the internal combustion engine 20. In some embodiments, the control system 11 is configured to initiate one or more protective measures via the power rationality diagnostic and protection module 190. FIG. 5 shows a method 400 that may be implemented by the control system 11 to initiate one or more engine protective measures. In operation 405, the control system 11 is configured to determine a frictional power loss amount. In various implementations, the frictional power loss amount may be determined by measuring the speed of the internal combustion engine 20 in operation 425 and estimating the frictional torque amount in operation 430. After determining the frictional power loss amount in operation 405, the control system 11 may determine an accessory power loss amount in operation 410. In various embodiments, the accessory power loss amount may be related to a load applied by the OEM system 12 (e.g., a cooling fan, a pump, an alternator, etc.) and / or any other accessory components in or coupled to the internal combustion engine 20.

[0043] In various embodiments, the accessory power loss amount can be based on the measured engine speed (determined in operation 425) and can be based on the estimated accessory torque amount determined in operation 435. Using the accessory power loss amount and the frictional power loss amount, the control system 11 can estimate a net engine power output amount in operation 415. In various embodiments, the net engine power output amount can also be based on a shaft power output amount (e.g., an engine dynamometer measurement) determined by the control system 11 in operation 440. Using the estimated net engine power output amount determined in operation 415, the control system 11 can estimate a first indicated engine power output and a first power output amount for the first fuel in operation 420. In various embodiments, the control system 11 can also estimate a commanded first fuel output. In some embodiments, the control system 11 is configured to estimate the commanded first fuel output by multiplying the determined thermal efficiency correction amount by the determined first fuel output estimate.

[0044] In some embodiments, determining the first fuel output estimate includes using a first lookup table. In various embodiments, the first lookup table is determined or referenced from the first fuel ECM and torque fueling calculation module 45. In some embodiments, the first lookup table is based on the first fuel rate and engine speed. In various embodiments, determining the thermal efficiency correction amount includes referencing a first set of lookup tables. In some embodiments, the first set of lookup tables is determined or referenced from the first fuel ECM and torque fueling calculation module 45. In various embodiments, the first set of lookup tables is based on a G / D of the internal combustion engine 20, a KPI associated with the internal combustion engine 20, and / or an intake manifold temperature within the internal combustion engine 20. In various embodiments, estimating the first power output amount for the second fuel includes subtracting the commanded first fuel output from the commanded engine power output.

[0045] The control system 11 may then estimate a second indicated engine power output and a second power output quantity for the second fuel in OPERATION 450. In various embodiments, the second total indicated engine power output and the second power output quantity for the second fuel may be based at least in part on the second fuel LHV value determined in OPERATION 445. In various embodiments, the LHV determined in OPERATION 445 may be based on the first power output quantity of the second fuel (determined in OPERATION 420), the total second fuel flow estimate, and the thermal efficiency correction amount. In some implementations, the LHV may be determined by the estimates. In various embodiments, the control system 11 may determine the LHV estimate by dividing the first power output quantity of the second fuel by a multiple of the second fuel flow estimate and the thermal efficiency correction amount. In various implementations, the resulting LHV is an instantaneous LHV amount. In some embodiments, the control system 11 may be configured to implement a learning algorithm to determine the LHV estimate from the instantaneous LHV amount.

[0046] In other embodiments, the second total indicated engine power output and the second power output quantity of the second fuel may additionally or alternatively be based on the estimated engine second fuel flow rate (determined in operation 453) and the estimated first fuel output quantity (determined in operation 455). In various embodiments, determining the second total indicated engine power output includes determining the product of the total second fuel flow rate estimate and the LHV estimate, and summing the product of the total second fuel flow rate estimate and the LHV estimate with the first fuel output estimate. In some embodiments, control system 11 may be configured to determine the first power output estimate for the second fuel based on the first total indicated engine power output, and to determine the second power output estimate for the second fuel based on the LHV estimate and the product of the estimated engine second fuel flow rate and a thermal efficiency parameter. In various embodiments, the thermal efficiency parameter corresponds to a thermal efficiency correction amount. Control system 11 may then determine a final second fuel output estimate based on the first power output estimate and the second power output estimate for the second fuel. In various embodiments, control system 11 may be configured to estimate the G / D of internal combustion engine 20. In various embodiments, control system 11 is configured to estimate the G / D of internal combustion engine 20 by dividing the final second fuel output estimate by the first total engine output estimate.

[0047] 5 , the control system 11 may then calculate a difference between the first total indicated engine load (e.g., power, torque, etc.) (determined in operation 420) and the second total indicated engine load (e.g., power, torque, etc.) (determined in operation 450) in operation 460. The control system 11 may then compare the difference between the first total indicated engine load and the second total indicated engine load (calculated in operation 460) to a predetermined threshold in operation 465. For example, in various implementations, the control system 11 may determine the difference between the predetermined threshold and the difference between the first total indicated engine load and the second total indicated engine load (i.e., a total indicated engine load delta). In various embodiments, the predetermined threshold may be set by the OEM and / or a user of the dual-fuel engine system 10.

[0048] Thus, if the difference between the total indicated engine load delta and the predetermined threshold is greater than a predetermined amount, the control system 11 may determine that the dual-fuel engine system 10 is operating in an abnormal or harmful condition. In various embodiments, the predetermined threshold is associated with a predetermined time period. In various embodiments, the predetermined threshold may be set, such as by the controller 18. For example, if the difference between the total indicated engine load delta and the predetermined threshold is greater than a predetermined amount for a predetermined time period, the control system 11 may determine that the dual-fuel engine system 10 is operating in an abnormal or harmful condition. Thus, in response to the control system 11 determining that the difference between the first total indicated engine load and the second total indicated engine load meets the predetermined threshold (or that the total indicated engine load delta exceeds a predetermined amount), the control system 11 may initiate (470) one or more engine protective measures. For example, the control system 11 may disable dual-fuel operation, perform a shutdown, and / or cause a reduction in engine speed, etc.

[0049] In other embodiments, the control system 11 may be configured to determine one or more second fuel power targets associated with the internal combustion engine 20. FIG. 6 shows a method 500 for determining a second fuel power target associated with the internal combustion engine 20. In operation 505, the control system 11 measures engine speed and estimates engine power output in operation 510. In various embodiments, the engine speed is sensed by sensors 95, 35, and / or 40. In some embodiments, the engine power output is a net engine power output. Based on the estimated engine power output from operation 510, the control system 11 may calculate a percentage of the rated power output of the internal combustion engine 20 (“percent power output”) in operation 515. The percent rated power output may be calculated by dividing the net engine power output by the rated engine power limit and multiplying by 100%. The control unit may also determine an intake manifold temperature (e.g., maximum intake manifold temperature) in operation 525 and an estimate of a KPI for the second fuel in operation 530. The control system 11 may determine a base second fuel displacement ratio (G / D) target for the internal combustion engine 20 in Operation 520. In various embodiments, the control system 11 determines the base G / D target based on engine speed, percent rated power, intake manifold temperature (determined in Operation 525), and estimated KPIs for the internal combustion engine 20. The control system 11 then determines a second fuel power target for the internal combustion engine 20 in Operation 535 based on the base second fuel displacement ratio target determined in Operation 520. In various embodiments, the second fuel power target is based on the base G / D target and the first indicated engine power estimate. In some embodiments, the control system 11 determines the first indicated engine power estimate by performing Operation 420 of method 400. In various embodiments, the control system 11 is configured to determine (e.g., calculate) the first indicated engine power based on an estimated amount of engine power and an amount of frictional power loss.

[0050] In various embodiments, the base G / D target determined in operation 520 is based on a first speed-based G / D target when the engine speed is above a threshold, which may be determined in operation 540, and a speed-based G / D target when the engine speed is below a threshold, which may be determined in operation 545. In various embodiments, at least one of the first speed-based G / D target or the second speed-based G / D target is determined based on an estimated KPI, such as intake manifold temperature (determined in operation 525) and / or methane number (determined in operation 530). In various embodiments, the first speed-based G / D target is a high-speed based G / D target, and the second speed-based G / D target is a low-speed based G / D target (i.e., lower than the first base G / D target). In some embodiments, the high-speed based G / D target is based on percent rated power, intake manifold temperature, and a KPI estimate. Similarly, the low-speed based G / D target is based on percent rated power, intake temperature, and a KPI estimate. Thus, the base G / D target determined in operation 520 is further determined by engine speed-based interpolation between the high-speed base G / D target and the low-speed base G / D target. In various embodiments, the high-speed base G / D target is determined from a first set of lookup tables and the low-speed base G / D target is determined from a second set of lookup tables (i.e., from lookup tables / database 145).

[0051] In various embodiments, the control system 11 may be configured to operate the dual-fuel engine system 10 to determine one or more second fuel injector commands for at least one engine bank in the internal combustion engine 20. FIG. 7 shows a method 600 for determining at least one second fuel injector command for at least one engine bank in the internal combustion engine 20. In operation 605, the control system 11 is configured to determine a second fuel flow target. In various implementations, the second fuel flow target is based on the second fuel output target determined in operation 625, the thermal efficiency estimate determined in operation 630, and the LHV determined in operation 635. In some implementations, the second fuel output target determined in operation 625 is determined by the control system 11 via method 500. In other implementations, the LHV determined in operation 635 is determined via the control system 11 performing one or more operations similar to or equivalent to operation 445. In other embodiments, the LHV determined in operation 635 is determined via an LHV sensor or lookup table based on a measured or estimated KPI. In various embodiments, determining the second fuel flow target in operation 605 includes dividing the second fuel output target by the thermal efficiency estimate and the LHV.

[0052] Control system 11 is configured to adjust the second fuel flow target at OPERATION 610 based on at least one of the measured second fuel temperature determined at OPERATION 640 and / or the measured second fuel injector pressure at OPERATION 645. In various embodiments, at least one of the second fuel temperature or the second fuel injector pressure is measured by sensors 35, 40, and / or 95. Using the adjusted second fuel flow target determined at OPERATION 610, control system 11 is configured to determine at least one base second fuel injector command at OPERATION 615. In various embodiments, the at least one base second fuel injector command is further determined based on the estimated G / D of internal combustion engine 20 determined at OPERATION 650 and the G / D target determined at OPERATION 655. In various implementations, the G / D target determined at OPERATION 655 is determined by control system 11 by performing one or more operations similar or equivalent to OPERATION 520. The control system 11 may then determine at least one second fuel injector command for at least one engine bank of the internal combustion engine 20 in Operation 620. In some embodiments, the second fuel output target is based on the first indicated engine power output estimate and the G / D target. In various implementations, the first indicated engine power output estimate is determined by the control system 11 by performing Operation 420. In some implementations, adjusting the second fuel flow target in Operation 610 includes calculating an adjusted second fuel flow target amount. In various embodiments, the second fuel flow target amount is based on a product of the second fuel flow target and at least one of the following: a first ratio of the measured second fuel temperature to a temperature reference quantity, or a second ratio of the measured second fuel injector pressure to a pressure reference quantity.

[0053] In various implementations, control system 11 may be further configured to estimate an overall second fuel flow rate. In various embodiments, the estimated overall second fuel flow rate is based on the measured second fuel injector pressure (determined in OPERATION 645), the measured second fuel temperature (determined in OPERATION 640), and at least one second fuel injector command for at least one engine bank. In some implementations, the at least one second fuel injector command for the at least one engine bank includes a left bank second fuel injector command (i.e., for the left bank 30) and a right bank second fuel injector command (i.e., for the right bank 31). In other implementations, determining the left bank second fuel injector command and determining the right bank second fuel injector command includes biasing the at least one second fuel injector command for the at least one engine bank to each of the left bank 30 and the right bank 31. In various embodiments, biasing the at least one second fuel injector command for at least one engine bank to each of the left bank 30 and the right bank 31 is based on an exhaust temperature differential associated with each of the left bank 30 and the right bank 31. In some embodiments, the exhaust temperature differential is measured by sensors 35, 40, and / or 95. In other embodiments, the exhaust temperature differential corresponds to the difference in the exhaust temperature measured at the left bank 30 and the exhaust temperature measured at the right bank 31. Thus, during operation of the dual engine system 10, the control system 11 may measure the exhaust temperature of the left bank 30, measure the exhaust temperature of the right bank 31, and determine the difference between the exhaust temperature of the left bank 30 and the exhaust temperature of the right bank 31. The control system 11 may then add a left bank adjustment amount to the at least one second fuel injector command for the at least one engine bank. In various embodiments, control system 11 adds a left bank adjustment amount to at least one second fuel injector command to determine a first adjusted base second fuel injector command based on the difference between the left bank exhaust temperature and the right bank exhaust temperature.Similarly, control system 11 may then add the right bank adjustment amount to at least one second fuel injector command for at least one engine bank. In various embodiments, control system 11 adds the right bank adjustment amount to at least one injector command for the second fuel to determine a second adjusted base second fuel injector command based on the difference between the left bank exhaust temperature and the right bank exhaust temperature. Control system 11 may then convert each of the first adjusted base second fuel injector command and the second adjusted base second fuel injector command into a left bank second fuel injector command and a right bank second fuel injector command, respectively.

[0054] In some implementations, determining at least one second fuel injector command for at least one engine bank in Operation 615 includes determining a feedforward input for a G / D PID controller operably coupled to the internal combustion engine 20. In various embodiments, the G / D PID controller is the controller 150. In some embodiments, the feedforward input is based on a lookup table. In various embodiments, the lookup table is determined or referenced from the first fuel ECM and torque fueling calculation module 45, the first fuel / air handling, aftertreatment, and fuel system reference determination and control module 60, and / or the indicated engine power and second fuel power estimation module 115. In various embodiments, the lookup table is based on at least one of a measured second fuel injector pressure, a measured second fuel temperature, or an adjusted second fuel flow target amount. In some embodiments, the control system 11 is further configured to determine at least one thermal control valve command. In various embodiments, the at least one thermal control valve command is associated with the heater control valve 195. In some embodiments, the at least one thermal control valve command is based on a measured second fuel temperature and / or a measured second fuel mass flow rate within internal combustion engine 20. In still other embodiments, control system 11 is further configured to adjust at least one second fuel temperature setpoint based on a measured KPI and / or an estimated KPI number. In various embodiments, the measured KPI is measured by sensors 35, 40, and / or 95. In some embodiments, the estimated KPI number is determined by KPI estimation module 125. In some implementations, the at least one second fuel temperature setpoint is based on an engine protection setpoint. In various embodiments, the engine protection setpoint is determined or set by OEM system 12, first fuel control system 14, or second fuel control system 16.

[0055] 8 illustrates a method 700 performed by the dual-fuel engine system 10. In various embodiments, the dual-fuel engine system 10 includes at least one PID controller coupled to the internal combustion engine 20 and the second fuel injector 28. In operation 705, the control system 11 determines a G / D estimate. In various embodiments, the G / D estimate is determined from the LHV and G / D estimation module 120. The control system 11 then determines a G / D target in operation 710. In various embodiments, the control system 11 determines the G / D target in operation 710 by performing one or more operations similar to or equivalent to operation 520 in method 500. In operation 715, the at least one PID controller is configured to receive a feedforward input in addition to the G / D estimate and the G / D target. In various embodiments, the feedforward input is based on a lookup table, which may be determined or referenced from first fuel ECM and torque fueling calculation module 45, first fuel / air handling, aftertreatment, and fuel system reference determination and control module 60, and / or indicated engine power and second fuel power estimation module 115. In some embodiments, the G / D target is determined from LHV and G / D estimation module 120. In operation 720, the at least one PID controller is configured to output at least one second fuel injector command. In operation 725, the at least one PID controller then biases the at least one second fuel injector command to each of left bank 30 and right bank 31. In various embodiments, the at least one PID controller biases the at least one second fuel injector command to each of left bank 30 and right bank 31 based on a difference between each of the left bank exhaust temperature (determined in operation 730) and the right bank exhaust temperature (determined in operation 735). In various embodiments, the exhaust temperature differential is determined in operation 740. In some embodiments, the at least one PID controller includes a first PID controller and a second PID controller.For example, a first PID controller may be configured to receive a feedforward input, a G / D estimate, and a G / D target (i.e., PID controller 150), and a second PID controller may be configured to bias at least one second fuel injector command to each of the left bank 30 and the right bank 31 (i.e., bank balancing PID 155).

[0056] In some embodiments, the dual-fuel engine system 10 includes an aftertreatment system operably coupled to the internal combustion engine 20 (i.e., controlled by the aftertreatment control system 85), a second fuel injection system including at least one second fuel injector 28 (i.e., controlled by the second fuel injector control module 110), and an air handling system operably coupled to the internal combustion engine 20 (i.e., controlled by the air handling control system 80). In some embodiments, the aftertreatment system is a selective catalytic reduction (SCR) and oxidation catalyst (OC) system. In some embodiments, the second fuel injection system is configured to independently control the second fuel injection in each of the left bank 30 and the right bank 31 (i.e., via the at least one second fuel injector 28). In other embodiments, the air handling system is configured to control airflow through the internal combustion engine 20. In some embodiments, the air handling system controls the airflow independently of the operating state of the internal combustion engine 20. In other embodiments, the airflow is based on a predetermined value obtained from a lookup table. In various embodiments, the lookup table is determined from or corresponds to a database 75 in module 60. In various embodiments, the predetermined value is related to a target temperature at at least one location of the aftertreatment system.

[0057] In various embodiments, the dual-fuel engine system 10 includes at least one second fuel injector 28 and one or more heaters operably coupled to the internal combustion engine 20. The at least one heater is configured to adjust the temperature (i.e., heat) of the second fuel flowing through the internal combustion engine 20. FIG. 9 shows a method 800 for controlling an operating state of a heater coupled to the internal combustion engine 20. In operation 805, the control system 11 is configured to determine a second fuel flow target. For example, the control system 11 is configured to determine the second fuel flow target via one or more operations similar to or equivalent to operation 605. In various implementations, the second fuel flow target determined in operation 805 can be based on one or more of a second fuel output target, an estimated thermal efficiency, and an LHV. For example, the second fuel flow target can be based on the second fuel output target determined in operation 820, the estimated thermal efficiency of the internal combustion engine 20 determined in operation 825, and the LHV determined in operation 830. Control system 11 can adjust the second fuel flow target at OPERATION 810 based on at least one of the measured second fuel temperature or the measured second fuel injector pressure. For example, control system 11 is configured to adjust the second fuel flow target at OPERATION 810 based on at least one of the measured second fuel temperature determined at OPERATION 835 or the measured second fuel injector pressure determined at OPERATION 840. In various implementations, the measured second fuel temperature determined at OPERATION 835 is determined by control system 11 by performing one or more operations similar or equivalent to OPERATION 640. In some embodiments, the measured second fuel temperature is determined via sensors 35, 40, and / or 95. In various embodiments, the measured second fuel injector pressure determined at OPERATION 840 is determined by control system 11 by performing one or more operations similar or equivalent to OPERATION 645. In some embodiments, the measured second fuel injector pressure determined at OPERATION 840 is determined by control system 11 by performing one or more operations similar or equivalent to OPERATION 645.Control system 11 may then control the operating state of heater 32 based on at least one of the measured second fuel temperature or the measured engine coolant temperature. In some embodiments, at least one of the measured second fuel temperature or the measured engine coolant temperature is determined via sensors 35, 40, and / or 95.

[0058] In some embodiments, control system 11 is configured to perform on / off control of heater 32 in response to a determination made regarding the measured second fuel temperature relative to one or more threshold temperatures. For example, control system 11 is configured to control operation of heater 32 in response to a determination that the measured second fuel temperature is lower than a first threshold temperature for a first period of time. Specifically, in some embodiments, control system 11 is configured to operate (i.e., turn on) heater 32 in response to a determination that the measured second fuel temperature (determined in operation 835) is lower than the first threshold temperature for a first period of time. In various embodiments, the first threshold temperature is set by OEM system 12, first fuel control system 14, or second fuel control system 16. In other embodiments, control system 11 is configured to control operation of heater 32 in response to a determination that the measured second fuel temperature is higher than a second threshold temperature for a second period of time. For example, control system 11 is configured to operate (i.e., turn off) heater 32 in response to determining that the measured second fuel temperature (determined in operation 835) is greater than a second threshold temperature for a second period of time. In various embodiments, the second threshold temperature is set by OEM system 12, first fuel control system 14, or second fuel control system 16.

[0059] Notwithstanding the embodiments described above with reference to FIGS. 1-9, various modifications and inclusions of those embodiments are contemplated and considered within the scope of the present disclosure.

[0060] It will be understood that the present technology may also include, but is not limited to, the features and combinations of features set forth in the following lettered paragraphs, and that the following paragraphs should not be construed as limiting the scope of the claims as appended hereto or as mandating that all such features must necessarily be included within the scope of such claims.

[0061] A. A method for controlling a dual fuel engine system, the method comprising: estimating a total indicated engine load, the total indicated engine load being based on the sum of the measured engine power and the power loss estimate; determining a total fueling amount based on engine speed and total indicated engine load, the total fueling amount including a fueling amount of the first fuel and a fueling amount of the second fuel; controlling a dual fuel engine system using the total fuel supply; A method comprising:

[0062] B. The method of paragraph A, wherein the method further includes determining a first updated total fuel supply amount based on a maximum value between the total fuel supply amount and the first fuel command for the first fuel.

[0063] C. The method of paragraph B, further comprising determining a second updated total fuel supply, wherein determining the second updated total fuel supply comprises subtracting the first fuel command for the first fuel from the first updated total fuel supply to determine a first fuel equivalent of the second fuel supply, and adding the first fuel equivalent of the second fuel supply to the second fuel command for the first fuel.

[0064] D. The method of paragraph A, wherein the step of controlling the dual fuel engine system includes the step of determining a first fuel system actuator command.

[0065] E. The method of paragraph A, wherein the step of determining the total fueling amount includes referencing a torque-to-fuel lookup table, the torque-to-fuel lookup table being based on engine speed and a commanded first fuel torque input.

[0066] F. The method of paragraph A, wherein the method further includes determining a power loss estimate based on the friction torque estimate, the accessory torque estimate, the charge air pumping torque, and the engine speed.

[0067] G. The method of paragraph F, wherein the method comprises: determining a friction torque estimate from a second lookup table based on the engine speed and the engine friction parameter; The method wherein the engine friction parameter is based on at least one of an oil temperature or a coolant temperature in a dual fuel engine system.

[0068] H. The method of paragraph E, wherein the method further includes determining the incidental torque estimate from a third lookup table, the third lookup table being based on engine speed and incidental torque parameters.

[0069] I. The method of paragraph H, wherein the method further includes determining an accessory torque parameter based on a cooling fan output or duty cycle commanded by the dual fuel engine system.

[0070] J. The method of paragraph B, wherein the method further includes determining at least one actuator command based on engine speed and at least one of the first updated total fueling amount or the second updated total fueling amount.

[0071] K. The method of paragraph A, further comprising determining a first fuel command for the first fuel from a torque-to-fuel lookup table, the torque-to-fuel lookup table being based on engine speed and a sum of the friction force estimate and a torque demand, the torque demand being set by an engine speed governor in a dual-fuel engine system.

[0072] L. A method for controlling a dual fuel engine system, the method comprising: estimating a total indicated engine load, the total indicated engine load being based on a sum of measured engine power, a friction force estimate, and an auxiliary power estimate; determining a total fueling amount from a first lookup table, the lookup table being based on engine speed and total indicated engine load; determining at least one updated total fuel supply amount based on the total fuel supply amount and an operational state of a dual fuel mode switch in the dual fuel engine system; determining a control input for at least one actuator in the dual fuel engine system; Equipped with The method wherein the control input is based on selecting a corresponding set of lookup tables associated with the at least one actuator, the set of lookup tables comprising a plurality of lookup tables, each of the plurality of lookup tables being based on engine speed and at least one updated total fuel delivery amount.

[0073] M. The method of paragraph L, wherein the at least one actuator is at least one of an air handling actuator, an aftertreatment actuator, or a first fuel system actuator.

[0074] N. The method of paragraph L, wherein the step of selecting a corresponding set of lookup tables includes determining a compressor inlet density, a second fuel displacement ratio in a dual engine system, and an operating state of a dual fuel mode switch.

[0075] O. The method of paragraph N, wherein the step of selecting a set of lookup tables further includes the step of selecting at least one of an air handling lookup table, an aftertreatment lookup table, or a fuel delivery lookup table.

[0076] P. The method of paragraph O, wherein the at least one updated fuel supply includes a first updated fuel supply and a second updated fuel supply, the first updated fuel supply corresponding to a maximum between the total fuel supply and the fuel command for the first fuel, and the second updated fuel supply is determined by subtracting the fuel command for the first fuel from the first updated total fuel supply to determine a first fuel equivalent of the fuel supply of the second fuel, and adding the equivalent fuel supply of the first fuel to the second fuel command for the first fuel.

[0077] Q. I have a dual fuel engine system. an internal combustion engine capable of operating in a dual fuel supply mode; at least one actuator operably coupled to the internal combustion engine; at least one controller in communication with the internal combustion engine and the at least one actuator; Equipped with At least one controller receiving a first input corresponding to engine speed and a second input corresponding to measured engine power; calculating a power loss estimate; determining a total fuel supply amount based on the measured engine power output and the power loss estimate; determining a first fuel command for a first fuel associated with the internal combustion engine based on at least the calculated speed governor command and the power loss estimate; determining at least one updated total fuel supply based on the total fuel supply and the first fuel command for the first fuel; selecting a lookup table set associated with the at least one actuator based on a second fuel displacement rate associated with the internal combustion engine, the lookup table set being based on engine speed and the at least one updated total fueling amount; sending an input to at least one actuator based on a set of lookup tables; 2. A system configured to:

[0078] R. The system of paragraph Q, wherein the at least one controller is further configured to determine the commanded first fuel torque input based on a sum of the friction force estimate and an engine speed torque demand, the engine speed torque demand corresponding to a difference between the engine speed and an engine speed target.

[0079] S. The system of paragraph Q, wherein the at least one controller is configured to determine a power loss estimate based on a friction torque estimate, an auxiliary torque estimate, a charge air pumping torque, and an engine speed.

[0080] T. The system of paragraph Q, wherein the at least one controller is further configured to select the lookup table based on a compressor inlet density.

[0081] U. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, the method comprising: determining a frictional power loss of an internal combustion engine of the dual fuel engine system, the frictional power loss being based on an engine speed of the internal combustion engine and a frictional torque estimate; determining an amount of incidental power loss in the output of the internal combustion engine, the amount of incidental power loss being based on engine speed and incidental torque estimates; estimating a net engine power output based on an auxiliary power loss and a shaft power output of the internal combustion engine; estimating an indicated power output for a first fuel; estimating a first indicated engine power output and a first power output for a second fuel based on the estimated net engine power output; A method for providing the above.

[0082] V. The method of paragraph U, wherein estimating the indicated power output for the first fuel comprises multiplying the determined thermal efficiency correction amount by the determined power output estimate for the first fuel.

[0083] W. The method of paragraph V, wherein determining the power output estimate for the first fuel comprises using a first lookup table, the first lookup table being based on a fuel rate for the first fuel and engine speed.

[0084] X. The method of paragraph V, wherein determining the thermal efficiency correction amount comprises consulting a first set of lookup tables, the first set of lookup tables being based on at least one of a substitution ratio for the second fuel, a knock tendency index, or an intake manifold temperature.

[0085] Y. The method of paragraph V, further comprising determining a lower heating value (LHV) estimate for the second fuel based on the first power output for the second fuel, the overall second fuel flow estimate, and a thermal efficiency correction.

[0086] Z. The method of paragraph Y, wherein the step of determining an LHV estimate comprises: The method comprising: dividing a first output for a second fuel by a multiple of a second fuel flow estimate and a thermal efficiency correction amount to determine an instantaneous LHV amount.

[0087] AA. The method of paragraph Z, further comprising applying a learning algorithm to the instantaneous LHV quantities to determine an LHV estimate.

[0088] BB. The method of paragraph Y, further comprising estimating a second total indicated engine power, the step of estimating the second total indicated engine power comprising: determining the product of the total flow estimate and the LHV estimate for the second fuel; determining a power output estimate for the first fuel plus the product of the total second fuel flow rate and the LHV estimate; A method for providing the above.

[0089] CC. The method of paragraph BB, further comprising determining a difference between the first total indicated engine power and the second total indicated engine power.

[0090] DD. The method of paragraph CC, further comprising initiating at least one engine protective measure based on a difference between the first total indicated engine power and the second total indicated engine power being greater than a threshold.

[0091] EE. The method of paragraph DD, further comprising setting the threshold to correspond to a predetermined period of time.

[0092] FF. The method of paragraph V, wherein estimating the first power output for the second fuel comprises subtracting the indicated power output for the first fuel from the indicated engine power output.

[0093] GG. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, the method comprising: estimating a net engine power output of the internal combustion engine of the dual-fuel engine system based on an incidental power loss of the internal combustion engine's power output and an estimated shaft power output of the internal combustion engine; determining a first total indicated engine power output based on a net engine power output and a frictional power loss of the internal combustion engine; determining a lower heating value (LHV) for a second fuel in an internal combustion engine, the LHV being a measured or estimated value; estimating a second total indicated engine power based on the LHV, the total flow estimate for the second fuel, and the power estimate for the first fuel; initiating at least one engine protective measure based on a difference between the first total indicated engine power and the second total indicated engine power being greater than a predetermined threshold; A method for providing the above.

[0094] HH. The method of paragraph GG, wherein the step of estimating a second total indicated engine power comprises: The method comprises determining a sum of a power estimate for the first fuel and the product of the total second fuel flow rate and the LHV.

[0095] II. The method of paragraph GG, determining a first power output estimate for a second fuel, the first power output estimate for the second fuel based on a first total indicated engine power; determining a second power output estimate for a second fuel, the second power output estimate for the second fuel based on the LHV and the product of the thermal efficiency estimate and an overall second fuel flow estimate; determining a final second fuel power output estimate based on the first power output estimate for the second fuel and the second power output estimate for the second fuel; A method further comprising:

[0096] JJ. The method of paragraph II, further comprising estimating a replacement rate for a second fuel, the step of estimating a replacement rate for the second fuel comprising: The method comprises dividing the final second fuel output estimate by the first power output estimate.

[0097] KK. A dual fuel engine system operable in a dual fuel supply mode, comprising: at least one controller in communication with the internal combustion engine, the internal combustion engine configured to operate using the first fuel and the second fuel; At least one controller receiving an input corresponding to an engine speed of an internal combustion engine; receiving inputs for calculating a net engine power estimate; calculating a percent rated power output of the internal combustion engine based on the engine speed and the estimated net engine power output; determining a base substitution rate target for the second fuel for the internal combustion engine based on engine speed, percent rated power, an intake manifold temperature within the internal combustion engine, and a knock tendency index estimate within the internal combustion engine; determining a second fuel output target for the internal combustion engine based on a base substitution rate target for the second fuel and the first indicated engine output estimate; 2. A system configured to:

[0098] LL. The system of paragraph KK, wherein the controller: determining a first speed-based displacement rate target for the second fuel when the engine speed is above a threshold based on the percent rated power, the intake manifold temperature, and the knock tendency index estimate; determining a second speed-based displacement rate target for the second fuel when the engine speed is below a threshold value based on the percent rated power, the intake manifold temperature, and the knock tendency index estimate; determining a base substitution rate target for the second fuel based on engine speed, a high speed base substitution rate target for the second fuel, and a low speed base substitution rate target for the second fuel; and determining a base replacement rate target for the second fuel by operation of the

[0099] MM. The system of paragraph LL, wherein a first speed-based replacement rate target for the second fuel is determined based on a first set of lookup tables and a second speed-based replacement rate target for the second fuel is determined based on a second set of lookup tables.

[0100] NN. The system of paragraph KK, wherein the controller is configured to determine the first indicated engine power output based on a net engine power output estimate and an amount of frictional power loss.

[0101] OO. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, the method comprising: determining a flow rate target of a second fuel for an internal combustion engine of the dual fuel engine system, the flow rate target of the second fuel being based on a power output target of the second fuel of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine; adjusting a flow target of the second fuel based on at least one of the measured second fuel temperature or the measured second fuel injector pressure; determining at least one base second fuel injector command based on the adjusted flow rate target of the second fuel, the second fuel substitution ratio estimate, and the second fuel substitution ratio target; determining a second fuel injector command for the at least one engine bank based on the at least one base second fuel injector command; A method for providing the above.

[0102] PP. The method of paragraph OO, further comprising estimating a total second fuel flow rate based on the measured second fuel injector pressure, the measured second fuel temperature, and at least one injector command for the second fuel for at least one engine bank.

[0103] QQ. The method of paragraph OO, wherein the at least one engine bank comprises a left bank and a right bank, and the at least one injector command for a second fuel for the at least one engine bank comprises a left bank second fuel injector command and a right bank second fuel injector command, and the step of determining the left bank second fuel injector command and the right bank second fuel injector command includes: The method includes biasing at least one injector command for a second fuel for at least one engine bank into each of the engine right bank and the engine left bank based on an exhaust temperature differential associated with each of the engine right bank and the engine left bank.

[0104] RR. The method of paragraph QQ, wherein the step of biasing at least one base second fuel injector command to each of the engine right bank and the engine left bank comprises: measuring a left bank exhaust temperature; measuring a right bank exhaust temperature; determining a difference between a right bank exhaust temperature and a left bank exhaust temperature; adding a left bank adjustment amount to at least one injector command for a second fuel for the at least one engine bank to determine a first adjusted based second fuel injector command based on a difference between the right bank exhaust temperature and the left bank exhaust temperature; adding a right bank adjustment amount to the at least one injector command for the second fuel for the at least one engine bank to determine a second adjusted base second fuel injector command based on a difference between the right bank exhaust temperature and the left bank exhaust temperature; converting each of the first adjusted base second fuel injector command and the second adjusted base second fuel injector command into a left bank second fuel injector command and a right bank second fuel injector command, respectively; A method for providing the above.

[0105] SS. The method of paragraph OO, wherein determining a flow target for the second fuel comprises dividing a power target for the second fuel by a thermal efficiency estimate and an LHV.

[0106] TT. The method of paragraph SS, wherein the power output target for the second fuel is based on the first indicated engine power output estimate and a second fuel displacement ratio target.

[0107] UU. The method of paragraph OO, wherein the step of adjusting the flow target of the second fuel comprises: 1. A method comprising: calculating an adjusted second fuel flow target amount, the adjusted second fuel flow target amount being a product of the flow target and at least one of a first ratio of a measured second fuel temperature to a temperature reference amount or a second ratio of a measured pressure to a pressure reference amount.

[0108] VV. The method of paragraph UU, wherein the step of determining at least one injector command for a second fuel for at least one engine bank comprises: The method includes determining a feedforward input for a second fuel displacement rate proportional-integral-derivative controller operably coupled to the internal combustion engine, the feedforward input being based on a lookup table that references at least one of a measured second fuel injector pressure, a measured second fuel temperature, or an adjusted second fuel flow target amount.

[0109] WW. The method of paragraph VV, comprising: The method further comprising adjusting at least one temperature setpoint for the second fuel based on at least one of the measured knock tendency index or the estimated knock tendency index.

[0110] XX. The method of paragraph WW, wherein at least one temperature setpoint for the second fuel is based on an engine protection setpoint.

[0111] YY. A dual-fuel engine system for an internal combustion engine configured to operate using a first fuel and a second fuel, the dual-fuel engine system comprising: at least one injector for a second fuel operably coupled to an internal combustion engine having a left bank and a right bank, the internal combustion engine being operable in a dual-fuel mode; at least one proportional-integral-derivative (PID) controller communicatively coupled to the internal combustion engine and to the at least one injector for the second fuel; Equipped with At least one PID controller receiving a feedforward input, a second refueling ratio estimate, and a second refueling ratio target; outputting at least one injector command for the second fuel based on the feedforward input; biasing at least one injector command for the second fuel into each of the right bank and the left bank based on an exhaust temperature differential associated with each of the right bank and the left bank; 2. A system configured to:

[0112] ZZ. The system of paragraph YY, wherein the at least one PID controller is configured to bias at least one injector command for the second fuel to each of the right bank and the left bank by performing an operation comprising: Measuring the left bank exhaust temperature; Measuring a right bank exhaust temperature; determining a difference between a right bank exhaust temperature and a left bank exhaust temperature; adding the left bank adjustment amount to the at least one injector command for the second fuel to determine a first adjusted injector command for the second fuel; adding the right bank adjustment amount to the at least one injector command for the second fuel to determine a second adjusted injector command for the second fuel; converting each of the first adjusted injector command for the second fuel and the second adjusted injector command for the second fuel into a left bank injector command for the second fuel and a right bank injector command for the second fuel, respectively; A system comprising:

[0113] AAA. The system of paragraph YY, wherein the at least one PID controller comprises a first PID controller and a second PID controller, the first PID controller configured to receive a feedforward input, a second fuel displacement ratio estimate, and a second fuel displacement ratio target, and the second PID controller configured to bias at least one injector command for the second fuel to each of the right bank and the left bank.

[0114] BBB. A system according to paragraph YY, an aftertreatment system operably coupled to the internal combustion engine, the aftertreatment system being a selective catalytic reduction (SCR) and oxidation catalyst (OC) system; an injection system for a second fuel operably coupled to the internal combustion engine, the injection system including at least one injector for the second fuel and configured to independently control injection of the second fuel for each of the left and right banks; an air handling system operably coupled to the internal combustion engine, the air handling system configured to control airflow through the internal combustion engine independently of an operating state of the internal combustion engine, the airflow being based on a predetermined value obtained from a lookup table, the predetermined value related to a target temperature at at least one location of the aftertreatment system; The system further comprises:

[0115] CCC. A dual fuel engine system operable in a dual fuel mode, the dual fuel engine system comprising: an internal combustion engine having at least one engine bank, the internal combustion engine configured to operate using a first fuel and a second fuel; at least one injector for a second fuel operably coupled to the internal combustion engine; at least one controller communicatively coupled to the internal combustion engine and to the at least one injector for the second fuel; Equipped with At least one controller determining a second fuel flow target for the internal combustion engine, the second fuel flow target based on a second fuel output target for the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine; adjusting the second fuel flow target based on at least one of the measured second fuel temperature or the measured second fuel injector pressure to determine an adjusted second fuel flow target for the dual fuel mode; determining at least one base second fuel injector command based on the adjusted second fuel flow target, the displacement rate estimate for the second fuel, and the displacement rate target for the second fuel; determining an injector command for a second fuel for the at least one engine bank based on the at least one base second fuel injector command; 2. A system configured to:

[0116] DDD. The system of paragraph CCC, wherein at least one controller: The system is further configured to determine a left bank second fuel injector command and a right bank second fuel injector command based on the at least one injector command for the second fuel.

[0117] EEE. The system of paragraph DDD, wherein the at least one controller is further configured to determine a second fuel flow target by dividing the second fuel output target by a thermal efficiency estimate and a lower heating value (LHV), the LHV being determined on a lookup table based on an estimated knock tendency index.

[0118] It should be noted that the use of the term "exemplary" and variations thereof herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and that such terms are not intended to imply that such embodiments are necessarily unusual or unique examples).

[0119] As used herein, the term "coupled" and variations thereof refer to the joining of two members directly or indirectly to one another. Such a joining can be static (e.g., permanent or fixed) or movable (e.g., removable or releasable). Such a joining can be achieved when two members are joined directly to one another, when two members are joined to one another using separate intervening members and any additional intermediate members joined to one another, or when two members are joined to one another using intervening members integrally formed with one of the two members as a single, unitary body. When "coupled" or variations thereof are modified by additional terms (e.g., directly coupled), the inclusive definition of "coupled" provided above is modified by the ordinary meaning of the additional terms (e.g., "directly coupled" means the joining of two members without any separate intervening members), resulting in a definition narrower than the inclusive definition of "coupled" provided above. Such a joining can be mechanical, electrical, or fluid.

[0120] References herein to the location of elements (e.g., "top," "bottom," "above," "below") are merely used to represent the orientation of various elements in the drawings. It should be noted that according to other exemplary embodiments, the orientation of various elements may differ, and such variations are intended to be encompassed by the present disclosure.

[0121] In some embodiments, the hardware and data processing components used to implement the various processes, operations, example logic, logic blocks, modules, and circuits described in connection with the embodiments disclosed herein, such as the controller hardware and data processing components (e.g., memory in controller 18, memory in OEM system 12, memory in first fuel control system 14, or memory in second fuel control system 16), may be implemented or performed using general-purpose single-chip or multi-chip processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some embodiments, particular processes and methods may be performed by circuitry specific to a given function. Memory (e.g., memory, memory unit, storage device) can include one or more devices (e.g., RAM, ROM, flash memory, hard disk storage) for storing data and / or computer code to complete or facilitate the various processes, layers, and modules described in this disclosure. Memory can be or include volatile or non-volatile memory and can include database components, object code components, script components, or any other type of information structure to support various activities and described in this disclosure.According to an exemplary embodiment, a memory (e.g., memory in controller 18, memory in OEM system 12, memory in first fuel control system 14, or memory in second fuel control system 16) is communicatively coupled to the processor via the processing circuitry and includes computer code for executing (e.g., by the processing circuitry or processor) one or more processes described herein.

[0122] The present disclosure contemplates methods and systems on any machine-readable medium for performing various operations, such as, for example, operations 305-360 of method 300, operations 405-470 of method 400, operations 505-545 of method 500, operations 605-655 of method 600, operations 705-740 of method 700, and operations 805-845 of method 800. Embodiments of the present disclosure may be implemented using existing computer processors, or by dedicated computer processors for suitable systems adapted for this or other purposes, or by hardwired systems. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media may be any available media that can be accessed by a general-purpose or special-purpose computer or other machine with a processor. By way of example, such machine-readable media may comprise RAM, ROM, EPROM, EEPROM, or other optical disk storage, magnetic disk storage, or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of machine-executable instructions or data structures and that can be accessed by a general-purpose computer or special-purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data that cause a general-purpose computer, special-purpose computer, or special-purpose processing machine to perform a certain function or group of functions.

[0123] Although the drawings and description may illustrate a particular order of method steps, the order of such steps may differ from that shown or described unless otherwise specified above. Also, unless otherwise specified above, two or more steps may be performed concurrently or with partial concurrency.

[0124] It is important to note that any element disclosed in one embodiment can be incorporated or utilized with any other embodiment disclosed herein. While only one example of elements from one embodiment that can be incorporated or utilized in another embodiment is described above, it should be appreciated that other elements of the various embodiments can be incorporated or utilized with any of the other embodiments disclosed herein. [Explanation of symbols]

[0125] 10 Dual fuel engine system 11 Control System 12 Machine control system (OEM system) 14 First Fuel Control System 16 Second fuel control system 18 Controller 20 Internal combustion engine 22 Accessories 24 output shaft 26 Manifold 28 Second fuel injector 30 Left Bank 31 Right Bank 32 Secondary fuel heater 33 Actuator 35 sensors 40 sensors 45 First Fuel Engine Control System (ECM) and Torque Fueling Calculation Module 50 Engine speed governor 55 Dual fuel mode switch 60 First Fuel Air Handling, Aftertreatment, and Fuel System Reference Determination and Control Module 65 Lookup Tables 75 databases 80 Air Handling Control System 85 Aftertreatment Control System 90 First Fuel Control System 95 Sensors 100 Second Fuel Heater Control Module 105 G / D target self-compensation module 110 Second Fuel Injector Control Module 115 Indicated Engine Power and Second Fuel Estimation Module 120 Second Fuel LHV and G / D Estimation Module 125 KPI estimation module 130 OEM Mechanical and Accessory Power Estimation Module 135 Velocity-Based G / D Target Interpolation Unit 140 G / D target limiter 145 databases 150 G / D Proportional-Integral-Derivative (PID) Controller 155 Bank Balancing PID Controller 160 Second fuel injector command converter 165 Second fuel flow estimator 170 databases 175 Torque vs. Power Calculation System 180 LHV Learning Algorithm 185 Second fuel output selector switch 190 Output Rationality Diagnostic and Protection Module 195 Heater Control Valve

Claims

1. 1. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, comprising: estimating a total indicated engine load, said total indicated engine load being based on the sum of the measured engine power and the power loss estimate; determining a total fueling amount based on engine speed and the total indicated engine load, the total fueling amount including a fueling amount for the first fuel and a fueling amount for the second fuel; controlling the dual fuel engine system using the total fuel supply; A method comprising:

2. 2. The method of claim 1, further comprising determining a first updated total fueling amount based on a maximum value between the total fueling amount and a first fuel command for the first fuel.

3. determining a second updated total fueling amount, wherein the determining the second updated total fueling amount comprises: subtracting the first fuel command for the first fuel from the first updated total fueling amount to determine a first fuel equivalent of a fueling amount of a second fuel; adding the first fuel equivalent of a fueling rate of a second fuel to a second fuel command for the first fuel; The method of claim 2 comprising:

4. The method of claim 1 , wherein controlling the dual fuel engine system comprises determining a fuel system actuator command for the first fuel.

5. 2. The method of claim 1, wherein the determining the total fueling amount step comprises referencing a torque-to-fuel lookup table, the torque-to-fuel lookup table being based on the engine speed and a commanded first fuel torque input.

6. 2. The method of claim 1, further comprising determining the power loss estimate based on a friction torque estimate, an accessory torque estimate, a charge air pumping torque, and the engine speed.

7. determining the friction torque estimate from a second lookup table, the second lookup table being based on the engine speed and engine friction parameters; The method of claim 6 , wherein the engine friction parameter is based on at least one of an oil temperature or a coolant temperature within the dual fuel engine system.

8. 6. The method of claim 5, further comprising determining the accessory torque estimate from a third lookup table, the third lookup table being based on the engine speed and accessory torque parameters.

9. 9. The method of claim 8, further comprising determining the accessory torque parameter based on a cooling fan power or duty cycle commanded by the dual fuel engine system.

10. 3. The method of claim 2, further comprising determining at least one actuator command based on the engine speed and at least one of the first updated total fueling amount or the second updated total fueling amount.

11. 2. The method of claim 1, further comprising determining the first fuel command for the first fuel from a torque-to-fuel lookup table, the torque-to-fuel lookup table being based on the engine speed and a sum of a friction force estimate and a torque demand, the torque demand being set by an engine speed governor in the dual fuel engine system.

12. 1. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, comprising: estimating a total indicated engine load, the total indicated engine load being based on a sum of measured engine power, a friction force estimate, and a collateral power estimate; determining a total fueling amount from a first lookup table, said lookup table being based on engine speed and said total indicated engine load; determining at least one updated total fueling amount based on the total fueling amount and an operational state of a dual fuel mode switch in the dual fuel engine system; determining a control input for at least one actuator in the dual fuel engine system; Equipped with the control input is based on selecting a corresponding set of lookup tables associated with the at least one actuator, the set of lookup tables comprising a plurality of lookup tables, each of the plurality of lookup tables being based on the engine speed and the at least one updated total fueling amount.

13. The method of claim 12 , wherein the at least one actuator is at least one of an air handling actuator, an aftertreatment actuator, or a fuel system actuator for the first fuel.

14. 13. The method of claim 12, wherein selecting the corresponding set of lookup tables comprises determining a compressor inlet density, a displacement rate for the second fuel in the dual engine system, and the operating state of the dual fuel mode switch.

15. The method of claim 14 , wherein selecting the set of lookup tables further comprises selecting at least one of an air handling lookup table, an aftertreatment lookup table, or a fueling lookup table.

16. 16. The method of claim 15, wherein the at least one updated fueling amount includes a first updated fueling amount and a second updated fueling amount, the first updated fueling amount corresponding to a maximum between the total fueling amount and a fuel command for the first fuel, and the second updated fueling amount is determined by subtracting the fuel command for the first fuel from the first updated total fueling amount to determine an equivalent fuel for the first fuel of the fueling amount for the second fuel, and adding the equivalent fueling amount for the first fuel to the second fuel command for the first fuel.

17. 1. A dual fuel engine configured to operate using a first fuel and a second fuel, comprising: an internal combustion engine capable of operating in a dual fuel supply mode; at least one actuator operably coupled to the internal combustion engine; at least one controller in communication with the internal combustion engine and the at least one actuator; Equipped with the at least one controller: receiving a first input corresponding to engine speed and a second input corresponding to measured engine power; calculating a power loss estimate; determining a total fuel supply amount based on the measured engine power output and the power loss estimate; determining a first fuel command for the first fuel associated with the internal combustion engine based on at least the calculated speed governor command and the power loss estimate; determining at least one updated total fueling amount based on the total fueling amount and the first fuel command for the first fuel; selecting a lookup table set associated with the at least one actuator based on a second fuel displacement rate associated with the internal combustion engine, the lookup table set being based on the engine speed and the at least one updated total fueling amount; sending an input to the at least one actuator based on the lookup table set; an engine system configured to:

18. 18. The system of claim 17, wherein the at least one controller is further configured to determine a commanded first fuel torque input based on a friction force estimate plus an engine speed torque demand, the engine speed torque demand corresponding to a difference between the engine speed and an engine speed target.

19. The system of claim 17 , wherein the at least one controller is configured to determine the power loss estimate based on a friction torque estimate, an accessory torque estimate, a charge air pumping torque, and the engine speed.

20. The system of claim 17 , wherein the at least one controller is further configured to select the lookup table based on a compressor inlet density.

21. 1. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, comprising: determining a frictional power loss amount of an internal combustion engine of the dual fuel engine system, the frictional power loss amount being based on an engine speed of the internal combustion engine and a frictional torque estimate; determining an amount of incidental power loss in the output of the internal combustion engine, the amount of incidental power loss being based on the engine speed and incidental torque estimates; estimating a net engine power output based on the auxiliary power loss and a shaft power output of the internal combustion engine; estimating an indicated power output for the first fuel; estimating a first indicated engine power output and a first power output for the second fuel based on the estimated net engine power output; A method comprising:

22. 22. The method of claim 21, wherein estimating the indicated power output for the first fuel comprises multiplying a determined power output estimate for the first fuel by a determined thermal efficiency correction amount.

23. 23. The method of claim 22, wherein determining the power output estimate for the first fuel comprises using a first lookup table, the first lookup table being based on a fuel rate for the first fuel and the engine speed.

24. 23. The method of claim 22, wherein determining the thermal efficiency correction amount comprises consulting a first set of lookup tables, the first set of lookup tables being based on at least one of a substitution ratio for the second fuel, a knock tendency index, or an intake manifold temperature.

25. 23. The method of claim 22, further comprising determining a lower heating value (LHV) estimate for the second fuel based on the first power output for the second fuel, an overall second fuel flow estimate, and the thermal efficiency correction.

26. determining the LHV estimate by:

26. The method of claim 25, comprising dividing the first output for the second fuel by a multiple of the second fuel flow estimate and the thermal efficiency correction amount to determine an instantaneous LHV amount.

27. 27. The method of claim 26, further comprising applying a learning algorithm to the instantaneous LHV quantity to determine the LHV estimate.

28. The method further includes estimating a second total indicated engine power, wherein the step of estimating the second total indicated engine power comprises: determining the product of the total flow estimate and the LHV estimate for the second fuel; determining the sum of the power output estimate for the first fuel and the product of the total second fuel flow rate and the LHV estimate; 26. The method of claim 25, comprising:

29. 30. The method of claim 28, further comprising determining a difference between the first total indicated engine power and the second total indicated engine power.

30. 30. The method of claim 29, further comprising initiating at least one engine protective measure based on the difference between the first total indicated engine power and the second total indicated engine power being greater than a threshold.

31. 31. The method of claim 30, further comprising setting the threshold to correspond to a predetermined period of time.

32. 23. The method of claim 22, wherein estimating the first power output for the second fuel comprises subtracting the indicated power output for the first fuel from the indicated engine power output.

33. 1. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, comprising: estimating a net engine power output of the internal combustion engine of the dual-fuel engine system based on an incidental power loss of the internal combustion engine's power output and an estimated shaft power output of the internal combustion engine; determining a first total indicated engine power output based on the net engine power output and frictional power losses of the internal combustion engine; determining a lower heating value (LHV) for the second fuel in the internal combustion engine, the LHV being a measured or estimated value; estimating a second total indicated engine power based on the LHV, the total flow estimate for the second fuel, and the power estimate for the first fuel; initiating at least one engine protective measure based on a difference between the first total indicated engine power and the second total indicated engine power being greater than a predetermined threshold; A method comprising:

34. estimating the second total indicated engine power; 34. The method of claim 33, comprising determining the sum of the power output estimate for the first fuel and the product of the total second fuel flow rate and the LHV.

35. determining a first power output estimate for the second fuel, the first power output estimate for the second fuel being based on the first total indicated engine power; determining a second power output estimate for the second fuel, the second power output estimate for the second fuel based on the LHV and a product of a thermal efficiency estimate and the overall second fuel flow estimate; determining a final second fuel output estimate based on the first power output estimate for the second fuel and the second power output estimate for the second fuel; 34. The method of claim 33, further comprising:

36. The method further includes a step of estimating a replacement rate for the second fuel, wherein the step of estimating the replacement rate for the second fuel includes:

36. The method of claim 35, comprising dividing the final second fuel output estimate by the first power output estimate.

37. 1. A dual fuel engine system operable in a dual fuel supply mode, comprising: at least one controller in communication with an internal combustion engine, the internal combustion engine configured to operate using a first fuel and a second fuel; the at least one controller: receiving an input corresponding to an engine speed of the internal combustion engine; receiving inputs for calculating a net engine power estimate; calculating a percent rated power output of the internal combustion engine based on the engine speed and the net engine power output estimate; determining a base substitution rate target for the second fuel for the internal combustion engine based on the engine speed, the percent rated power, an intake manifold temperature within the internal combustion engine, and a knock tendency index estimate within the internal combustion engine; determining a second fuel output target for the internal combustion engine based on the base substitution rate target for the second fuel and a first indicated engine output estimate; 1. A dual fuel engine system configured to:

38. The controller: determining a first speed-based replacement rate target for the second fuel when the engine speed exceeds a threshold value based on the percent rated power, the intake manifold temperature, and the knock tendency index estimate; determining a second speed-based replacement rate target for the second fuel when the engine speed is below the threshold based on the percent rated power, the intake manifold temperature, and the knock tendency index estimate; determining the base replacement rate target for the second fuel based on the engine speed, the high speed base replacement rate target for the second fuel, and the low speed base replacement rate target for the second fuel; 38. The system of claim 37, configured to determine the base replacement rate target for the second fuel by performing the operations of:

39. 39. The system of claim 38, wherein the first speed-based replacement rate target for the second fuel is determined based on a first set of lookup tables, and the second speed-based replacement rate target for the second fuel is determined based on a second set of lookup tables.

40. 38. The system of claim 37, wherein the controller is configured to determine the first indicated engine power output based on the net engine power output estimate and an amount of frictional power loss.

41. 1. A method for controlling a dual fuel engine system configured to operate using a first fuel and a second fuel, comprising: determining a flow rate target for the second fuel for an internal combustion engine of the dual fuel engine system, the flow rate target for the second fuel being based on a power output target for the second fuel of the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine; adjusting the flow target of the second fuel based on at least one of a measured second fuel temperature or a measured second fuel injector pressure; determining at least one base second fuel injector command based on the adjusted flow target for the second fuel, a second fuel substitution ratio estimate, and a second fuel substitution ratio target; determining a second fuel injector command for at least one engine bank based on the at least one base second fuel injector command; A method comprising:

42. 42. The method of claim 41, further comprising estimating a total second fuel flow rate based on the measured second fuel injector pressure, the measured second fuel temperature, and the at least one injector command for the second fuel for the at least one engine bank.

43. the at least one engine bank comprises a left bank and a right bank, and the at least one injector command for the second fuel for the at least one engine bank comprises a left bank second fuel injector command and a right bank second fuel injector command, and determining the left bank second fuel injector command and the right bank second fuel injector command comprises:

42. The method of claim 41, comprising biasing the at least one injector command for the second fuel for the at least one engine bank to each of the right engine bank and the left engine bank based on an exhaust gas temperature differential associated with each of the right engine bank and the left engine bank.

44. biasing the at least one base second fuel injector command to each of the right engine bank and the left engine bank; measuring a left bank exhaust temperature; measuring a right bank exhaust temperature; determining a difference between the right bank exhaust temperature and the left bank exhaust temperature; adding a left bank adjustment amount to the at least one injector command for the second fuel for the at least one engine bank to determine a first adjusted base second fuel injector command based on the difference between the right bank exhaust temperature and the left bank exhaust temperature; adding a right bank adjustment amount to the at least one injector command for the second fuel for the at least one engine bank to determine a second adjusted base second fuel injector command based on the difference between the right bank exhaust temperature and the left bank exhaust temperature; converting each of the first adjusted base second fuel injector command and the second adjusted base second fuel injector command into the left bank second fuel injector command and the right bank second fuel injector command, respectively; 44. The method of claim 43, comprising:

45. 42. The method of claim 41, wherein determining the flow target for the second fuel comprises dividing the power target for the second fuel by the thermal efficiency estimate and the LHV.

46. 46. ​​The method of claim 45, wherein the power target for the second fuel is based on a first indicated engine power estimate and the second fuel replacement ratio target.

47. adjusting the flow rate target of the second fuel; 42. The method of claim 41, comprising calculating an adjusted second fuel flow target amount, the adjusted second fuel flow target amount being a product of the flow target and at least one of a first ratio of the measured second fuel temperature to a temperature reference quantity or a second ratio of the measured pressure to a pressure reference quantity.

48. determining at least one injector command for the second fuel for the at least one engine bank; 48. The method of claim 47, comprising determining a feedforward input for a second fuel displacement rate proportional-integral-derivative controller operatively coupled to the internal combustion engine, the feedforward input based on a lookup table that references at least one of the measured second fuel injector pressure, the measured second fuel temperature, or the adjusted second fuel flow target amount.

49. 49. The method of claim 48, further comprising adjusting at least one temperature setpoint for the second fuel based on at least one of a measured knock tendency index or an estimated knock tendency index.

50. 50. The method of claim 49, wherein the at least one temperature setpoint for the second fuel is based on an engine protection setpoint.

51. 1. A dual fuel engine system for an internal combustion engine configured to operate using a first fuel and a second fuel, comprising: at least one injector for the second fuel operably coupled to the internal combustion engine having a left bank and a right bank, the internal combustion engine being operable in a dual fuel mode; at least one proportional-integral-derivative (PID) controller communicatively coupled to the internal combustion engine and the at least one injector for the second fuel; Equipped with The at least one PID controller receiving a feedforward input, a second refueling ratio estimate, and a second refueling ratio target; outputting at least one injector command for the second fuel based on the feedforward input; biasing the at least one injector command for the second fuel to each of the right bank and the left bank based on an exhaust gas temperature differential associated with each of the right bank and the left bank; 1. A dual fuel engine system configured to:

52. the at least one PID controller is configured to bias the at least one injector command for the second fuel to each of the right bank and the left bank by performing an operation comprising: Measuring the left bank exhaust temperature; Measuring a right bank exhaust temperature; determining a difference between the right bank exhaust temperature and the left bank exhaust temperature; adding a left bank adjustment amount to the at least one injector command for the second fuel to determine a first adjusted injector command for the second fuel; adding a right bank adjustment amount to the at least one injector command for the second fuel to determine a second adjusted injector command for the second fuel; converting each of the first adjusted injector command for the second fuel and the second adjusted injector command for the second fuel into the left bank injector command for the second fuel and the right bank injector command for the second fuel, respectively; 52. The system of claim 51, comprising:

53. 52. The system of claim 51, wherein the at least one PID controller comprises a first PID controller and a second PID controller, the first PID controller configured to receive the feedforward input, the second fuel replacement ratio estimate, and the second fuel replacement ratio target, and the second PID controller configured to bias the at least one injector command for the second fuel to each of the right bank and the left bank.

54. an aftertreatment system operably coupled to the internal combustion engine, the aftertreatment system being a selective catalytic reduction (SCR) and oxidation catalyst (OC) system; an injection system for the second fuel operably coupled to the internal combustion engine, the injection system including the at least one injector for the second fuel and configured to independently control injection of the second fuel for each of the left bank and the right bank; an air handling system operably coupled to the internal combustion engine, the air handling system configured to control airflow through the internal combustion engine independently of an operating state of the internal combustion engine, the airflow being based on a predetermined value obtained from a look-up table, the predetermined value related to a target temperature at at least one location of the aftertreatment system; 52. The system of claim 51, further comprising:

55. 1. A dual fuel engine system capable of operating in a dual fuel mode, comprising: an internal combustion engine having at least one engine bank, the internal combustion engine configured to operate using a first fuel and a second fuel; at least one injector for the second fuel operably coupled to the internal combustion engine; at least one controller communicatively coupled to the internal combustion engine and the at least one injector for the second fuel; Equipped with the at least one controller: determining a second fuel flow target for the internal combustion engine, the second fuel flow target being based on a second fuel output target for the internal combustion engine, an estimated thermal efficiency of the internal combustion engine, and a lower heating value (LHV) within the internal combustion engine; adjusting the second fuel flow target based on at least one of a measured second fuel temperature or a measured second fuel injector pressure to determine an adjusted second fuel flow target for the dual fuel mode; determining at least one base second fuel injector command based on the adjusted second fuel flow target, the replacement rate estimate for the second fuel, and the replacement rate target for the second fuel; determining an injector command for the second fuel for the at least one engine bank based on the at least one base second fuel injector command; 1. A dual fuel engine system configured to:

56. the at least one controller:

56. The system of claim 55, further configured to determine a left bank second fuel injector command and a right bank second fuel injector command based on the at least one injector command for the second fuel.

57. 57. The system of claim 56, wherein the at least one controller is further configured to determine the second fuel flow target by dividing the second fuel output target by a thermal efficiency estimate and a lower heating value (LHV), the LHV being determined on a lookup table based on an estimated knock tendency index.

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